Radiofrequency amplifying system



June 7, 1932. w. KQMCIVER 1,861,707

RADIOFREQUENCY AMPLIFYING SYSTEM Filed Jan. 20. 1927 2 Sheets-Sheet, 1

June-7, 1932. V w, MOIVER 1,861,707

RADIOFREQUENCY AMPLIFYING SYSTEM Filed Jan. 20. 1927 2 Sheets-Sheet 2 Patented June 7, 1932 UNITED STATES PATENT OFFICE COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS RADIOFREQUENCY AMPLIFYING SYSTEM.

Application filed January 20, 1927. Serial No. 162,275.

My invention relates to radio frequency am lifying systems.

ne of the objects of my lnventlon is to provide means for use in such a system, which, as the grid circuits are tuned for the various wave lengths, will automatically regulate the energy transfer between circuit-s in such manner that substantially an equal 7 amount of energy will be transferred to the 0" grid circuit from the preceding circu at all frequencies, said quantity of energy to be the maximum which can be transferred without causing self sustained oscillations.

A further object of my inventionis to provide, in addition to the means for automatic equalizing coupling referred to, an additional energy transferring connection in parallel with the automatic coupler so that the coupling can be increased when desired. Th1s g supplemental energy transferring device may be of advantage, for instance, in the case of weak signals, by bringing the circuit nearer the point of oscillation than the means for A automatic equalization will do, for the purpose of increasing the volume.

A further object of my invention is to provide, in addition to a means for the automatic equalizing coupling referred to, a high 7 impedance in that branch of the plate circuit connected with the'source of plate volta e in order to cause a maximum transfer 0 high frequency energy through the equalizing coupling condenser to the grid circuit.

Further ob ects will appearfrom the description and claims.

In the drawings, in which several circuits embodying my invention, are shown,

Figure. 1 is a clrcuit diagram of a radioj frequency amplifying system embodying my invention;

Fig. 2 is a plan View showing the tuning condenser and the equalizing condenser;

Fig. 3 is a front elevation of parts shown in Fig. 2;

Fig. 4 shows another form of circuit diagram embodyingm invention; and

Fig. 5 shows stil another form of circuit diagram embodying my invention.

Referring now to the drawings in detail,

" and first to Figs. 1, 2, and 3, the circuit diagram of Fig. 1 shows two stages of radio frequency amplification and a detector. The grid circuit of each radio frequency ampliiier tube and also of the detector tube comprises an inductance coil 1 and a variable condenser 2, by means of which the grid circuit may be tuned. The grid circuit of the first amplifier tube 3 is connected with the aerial circuit 4 by means of an adjustable equalizmg condenser 5. transfer between the aerial and grid circuit may increase as the grid circuit is tuned for stations of lower frequency, a mechanical coupling 5a is provided between the movable element of the equalizing condenser 5 and the movable element of the tuning condenser 2.

The grid circuit of the second amplifier tube 6 is coupled with the plate circuit of the preceding tube by means of a variable equalizing coupling condenser 7. In order that the energy transfer between the plate circuit of the lirst tube and the grid circuit of the succeeding tube may be increased a-utomatically as the tuning condenser of the second tube is tuned for stations of lower fre-- quency, a mechanical coupling 8 is provided between the tuning condenser 2 and the equalizing coupling condenser 7. In a similar manner an equalizing condenser 9 is provided between the grid circuit of the detector tube 10 and the plate circuit of the preceding amplifier 6. A mechanical coupling 11 is provided between the equalizing condenser 9 and the tuning condenser 2 of the grid circuit of the detector. In order to cause a maximum transfer of high frequency energy through the equalizing condenser to the grid circuit a high impedance 12 is provided in that part of the plate circuit connected to the source of plate Voltage which impedance, as shown, is in the form of high resistances.

I have shown a second adjustable condenser 12a in parallel with the adjustable equalizing condenser 9 which also acts as a means for transferring energy between the gri d circuit of the detector 10 and the plate circuit of the preceding tube 6. This condenser may be manually adjusted independ- In order that the energy f ently of the tuning condenser and the equalizing condenser. This supplemental condenser enables the transfer of energy to be increased to bring the circuit up to the point of oscillation in order to increase the volume of weak signals for distant stations and the like. Similar supplemental coupling condensers might be similarly placed in parallel with coupling condensers 7 and 5.

I An outlet 12?) is provided from the'detector tubes to an audio frequency amplifier. In practice I have secured good results using inductance coils of 50 turns "of No. 26 B. & S. wire for an inductance, and tuning condensers having a maximum capacity of .00035 M. F., anequalizing condenser between the aerial and grid circuit of the first amplifier having a maximum capacity of .00008, equalizing condensers between the plate and grid circuits having maximum capacity of .00002, and resistances in the plate circuits having values between 12 and 75 megohms. It is problem,- however, that satisfactory results could be secured using inductances, capacities and resistances widely different from those stated above.

-The grid circuit of the detector tube is provided with any usual or suitable grid condenser 13 and grid leak 14, although both may be omitted if a negative grid bias of suitable voltage is employed.

In Figs. 2 and 3 I have shown a unit comprising a tuning condenser 2 and an equalizing condenser 7 mechanically connected, which I have found satisfactory in use. The tuning condenser 2 may beof -any usual or suitable type adjusted by thethumb-piece 15 through the friction drive transmission 16. The equalizing'condenser 7 may be mounted on an insulating plate 17 secured in the rear ofthe tuning condenser 2. For equalizing between tubes I use a condenser having but one stator plate 18 and one rotor plate 19. The rotorplate 19 of the equalizing condenser 7 may be mounted on the same shaft as that on which the rotor plates 20 of the tuning condenser 2 are mounted but insulated from said shaft, so that the capacity of the equalizing condenser 7 increases or decreases as the capacity of the tuning condenser'2 increases or decreases. The relation of the rotor and stator .platesin the two condensers is such that the maximum overlap of the plates of the equalizing condenser occurs at the same 1 towhic h the grid circuit is tuned.

In addition to the usual adjustment of the equalizing condenser, I provide an additional adjustment by means of which I am enabled to vary the distance between the rotor plate 19 and the stator plate 18. The construction which I have employed for this purpose comprises a plurality of uses 2]., preferably three or more, secured to the insulating plate 17 and a pluralit of pairs of nuts 22 threaded on thesest'u between which nuts the stator plate 18 is clamped. By ad ust.ng these nuts on the threaded studs the distance between "the stator plate 18 and the rotor plate 19 may be adjusted and if desired the stator plate may be adjusted to lie at a slight angle with respect to the rotor plate. By

means of this adjustment the capacity curve of the condenser may be raised or lowered or its inclination changed. This construction enables the energy transferring effect between the grid circuit of a tube and the preceding circuit to be increased or diminished independently of the automatic equalization so that if it is found that the energy transfer is more or less than that desired this effect can be diminished or increased at will to secure just the right effect. I have shown an insulating plate 23 secured in the rear of the equalizing condenser on which an inductance coil may be mounted if desired.

In Fig. 4 I have shown another form of circuit substantially like that shown in Fig. 1 except that a commonstator is provided. for the rotor plates of-the tuningand equalizing condensers.

In Fig.5 I have shown another form of circuit which issubstantia'llythe same asthat shown in Fig. l'except that here Ihave connected thestator plate of the equalizing condenser at an intermediate point of the inductioncoil 1. If it is desired, two or more of the tuning condensers -may be mechanically connected to reduce the number of tuning knobs to'simplify'the control.

The operation of *the circuit has been out lined in connection with "the -des'criptionjof the circuit. With regard to the action of-the mechanically coupled tuning cond'e'ns'ers and equalizing condensers the underlying idea is that the energy transferring effect of the equalizing condenser is automatically increased as the tuning condenser is'tunedffor waves of lower frequency. This automatically equalizes 'the transfer ofenergy which tends to decrease with the lower frequencies if the connection remains unchanged. This automatic variation of condenser connection is provided both between the aerial and-the grid of the first amplifier and between the plate and grid circuits'of the tubes.

The high impedances in the plate circuits as indicated above, serve to causes. maximum transfer of high frequencyenergy-throngh the equalizingcondenser to theggrid circuit by preventing its escape thru the source of plate voltage.

The supplemental energy transferring condenser 12a enables the operator to bring up the energy transferring effect when desired to bring the circuit substantially up to the point of oscillation for Weak signals.

I claim:

1. A tuned radio frequency amplifying system comprising means for coupling the plate circuit of one tube with the grid circuit of a succeeding tube and equalizing the transfer of energy between said circuits at all frequencies, said grid circuit having manually adjustable tuning means, said equalizing means comprising a condenser having adjusting means for varying the overlap of the opposing plates and having adjusting means for varying the distance between opposing plates, and means whereby manual adjustment of said tuning means will automatically cause adjustment of one of the adj usting means of the equalizing condenser to equalize the transfer of energy at all frequencies.

2. A tuned radio frequency amplifying system comprising means for coupling the plate circuit of one tube with the grid circuit of a succeeding tube and equalizing the transfer of energy between said circuits at all frequencies, said grid circuit having manually adjustable tuning means, said equalizing means comprising a condenser having adj usting means for varying the overlap of the opposing plates and having adjusting means for varying the distance between opposing plates, and means whereby manual adjustment of said tuning means will automatically cause adjustment of the means for varying the overlap of the opposing plates of the equalizing condenser to equalize the transfer of energy at all frequencies.

In Witness whereof, I have hereunto subscribed my name.

WILLIAM K. MoIVER. 

